A health and fitness fanatic, he may have been injured or become disoriented in unfamiliar territory as daytime temperatures soar to 39C.

Search and rescue teams conducted a land and air search of the area surrounding the station on Wednesday but failed to find any sign of him.

An aerial and land search resumed at first light this morning. He had spent at least one night, and possibly two, alone and exposed to the elements.

Sergeant Dave Perry from the Stock Squad said the property owner contacted police at 10.30am Wednesday.

"The owner of the property has gone to probably chase him out of bed because he wasn't out of bed yet," Sgt Perry said.

"She went to his room (and) he's not there.

"The property missing from his room included a backpack and a pair of joggers."

There had been no cause for concern before he went missing.

"There's no indication of anything that would cause him to go away," Sgt Perry said.

"Hes really into fitness. He jogged on a number of occasions. It is possible he may have been jogging on this occasion and become disoriented.

"We're not basing that on anything other than the fact he's been jogging previously."

Sam, who is from London and went to Brighton College, had been experiencing the Outback during an Australian adventure that had previously included a visit to the Gold Coast.

His sister Rebecca has written on Facebook about the family's concerns.

"The helicopter and quad bikes have been out looking for him," Rebecca wrote yesterday.

"He has been missing for more than 24 hours and the search has been called off because it is now night time in Australia so he will be out there for another night.

"Please please anyone contact me if you hear ANYTHING."

In later posts she added: "Thanks so much for all your messages regarding Sam. Still no further news but we have the helicopter going out again in the morning, Aus time, and hundreds of people going on a voluntary search party. will keep you all posted. X.

"Would be a great birthday present if my brother would just turn up and ask what all the fuss is about!"

Residents from surrounding properties have been using their own light aircraft to assist in the search.

The 180cm tall backpacker, who has a muscular build and short dark hair, is believed to have been wearing white shorts and a white shirt.